arXiv subjects

P. Jakobsson

Publications and source records attributed to P. Jakobsson.

At least 109 records · Page 6Linked to original sources

arXiv2012

Rapid-response mode VLT/UVES spectroscopy of super iron-rich gas exposed to GRB 080310. Evidence of ionization in action and episodic star formation in the host

We analyse high-resolution near-UV and optical spectra of the afterglow of GRB 080310, obtained with the Very Large Telescope Ultraviolet and Visual Echelle Spectrograph (VLT/UVES), to investigate the circumburst environment and the interstellar medium of the gamma-ray burst (GRB) host galaxy. The VLT rapid-response mode (RRM) enabled the observations to start only 13 minutes after the Swift trigger and a series of four exposures to be collected before dawn. A low neutral-hydrogen column-density (log N (HI) = 18.7) is measured at the host-galaxy redshift of z = 2.42743. At this redshift, we also detect a large number of resonance ground-state absorption lines (e.g., CII, MgII, AlII, SiII, CrII, CIV, SiIV), as well as time-varying absorption from the fine-structure levels of FeII. Time-varying absorption from a highly excited FeIII energy level (7S3), giving rise to the so-called UV34 line triplet, is also detected, for the first time in a GRB afterglow. The CrII ground-state and all observed FeII energy levels are found to depopulate with time, whilst the FeIII 7S3 level is increasingly populated. This absorption-line variability is clear evidence of ionization by the GRB, which is for the first time conclusively observed in a GRB afterglow spectrum. We derive ionic column densities at each epoch of observations by fitting absorption lines with a four-component Voigt-profile model. We perform CLOUDY photo-ionization modelling of the expected pre-burst ionic column densities, to estimate that, before the onset of the burst, [C/H] = -1.3 \pm 0.2, [O/H] < -0.8, [Si/H] = -1.2 \pm 0.2, [Cr/H] = +0.7 \pm 0.2, and [Fe/H] = +0.2 \pm 0.2 for the integrated line profile, indicating strong overabundances of iron and chromium. For one of the components, we observe even more extreme ratios of [Si/Fe] \leq -1.47 and [C/Fe] \leq -1.74. [abridged]

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arXiv2012

The optically unbiased GRB host (TOUGH) survey. VI. Radio observations at z<1 and consistency with typical star-forming galaxies

The objective of this paper is to determine the level of obscured star formation activity and dust attenuation in a sample of gamma-ray burst (GRB) hosts; and to test the hypothesis that GRB hosts have properties consistent with those of the general star-forming galaxy populations. We present a radio continuum survey of all z<1 GRB hosts in The Optically Unbiased GRB Host (TOUGH) sample supplemented with radio data for all (mostly pre-Swift) GRB-SN hosts discovered before October 2006. We present new radio data for 22 objects and have obtained a detection for three of them (GRB 980425, 021211, 031203; none in the TOUGH sample), increasing the number of radio-detected GRB hosts from two to five. The star formation rate (SFR) for the GRB 021211 host of ~825 Mo yr^-1, the highest ever reported for a GRB host, places it in the category of ultraluminous infrared galaxies. We found that at least 63% of GRB hosts have SFR < 100 Mo yr^-1 and at most 8% can have SFR > 500 Mo yr^-1. For the undetected hosts the mean radio flux (<35 uJy 3sigma) corresponds to an average SFR < 15 Mo yr^-1. Moreover, ~88% of the z<1 GRB hosts have ultraviolet dust attenuation A_UV < 6.7 mag (visual attenuation A_V < 3 mag). Hence we did not find evidence for large dust obscuration in a majority of GRB hosts. Finally, we found that the distributions of SFRs and A_UV of GRB hosts are consistent with those of Lyman break galaxies, Halpha emitters at similar redshifts and of galaxies from cosmological simulations. The similarity of the GRB population with other star-forming galaxies is consistent with the hypothesis that GRBs, a least at z<1, trace a large fraction of all star formation, and are therefore less biased indicators than once thought.

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arXiv2012

GRB 100219A with X-shooter - abundances in a galaxy at z = 4.7

Abundances of galaxies at redshifts z > 4 are difficult to obtain from damped Ly α (DLA) systems in the sightlines of quasars (QSOs) due to the Ly α forest blanketing and the low number of high-redshift quasars detected. Gamma-ray bursts (GRBs) with their higher luminosity are well suited to study galaxies out to the formation of the first stars at z > 10. Its large wavelength coverage makes the X-shooter spectrograph an excellent tool to study the interstellar medium (ISM) of high redshift galaxies, in particular if the redshift is not known beforehand. Here we determine the properties of a GRB host at z = 4.66723 from a number of resonant low- and high ionization and fine-structure absorption lines. This is one of the highest redshifts where a detailed analysis with medium-resolution data has been possible. We detect one intervening system at z = 2.18. The velocity components of the absorption lines are fitted with Voigt-profiles and we determine a metallicity of [M/H] = -1.0 \pm 0.1 using S. The absorption lines show a complicated kinematic structure which could point to a merger in progress. Si II* together with the restframe UV energy release determined from GROND data gives us the distance of 0.3 to 1 kpc of the absorbing material from the GRB. We measure a low extinction of AV = 0.24 \pm 0.06 mag using X-ray spectral information and the flux calibrated X-shooter spectrum. GRB-DLAs have a shallower evolution of metallicity with redshift than QSO absorbers and no evolution in HI column density or ionization fraction. GRB hosts at high redshift might continue the trend towards lower metallicities in the LZ-relation with redshift, but the sample is still too small to draw a definite conclusion. While the detection of GRBs at z > 4 with current satellites is still difficult, they are very important for our understanding of the early epochs of star- and galaxy-formation.

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arXiv2012

Star formation in the early universe: beyond the tip of the iceberg

We present late-time Hubble Space Telescope imaging of the fields of six Swift GRBs lying at 5.0 90% confidence. Although it is not yet possible to make stronger statements, in the future, with larger samples and a fuller understanding of the conditions required for GRB production, studies like this hold great potential for probing the nature of star formation, the shape of the galaxy luminosity function, and the supply of ionizing photons in the early universe.

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arXiv2012

The optically unbiased GRB host (TOUGH) survey. III. Redshift distribution

We present 10 new gamma-ray burst (GRB) redshifts and another five redshift limits based on host galaxy spectroscopy obtained as part of a large program conducted at the Very Large Telescope (VLT). The redshifts span the range 0.345 < z < 2.54. Three of our measurements revise incorrect values from the literature. The homogeneous host sample researched here consists of 69 hosts that originally had a redshift completeness of 55% (with 38 out of 69 hosts having redshifts considered secure). Our project, including VLT/X-shooter observations reported elsewhere, increases this fraction to 77% (53/69), making the survey the most comprehensive in terms of redshift completeness of any sample to the full Swift depth, analyzed to date. We present the cumulative redshift distribution and derive a conservative, yet small, associated uncertainty. We constrain the fraction of Swift GRBs at high redshift to a maximum of 14% (5%) for z > 6 (z > 7). The mean redshift of the host sample is assessed to be > 2.2, with the 10 new redshifts reducing it significantly. Using this more complete sample, we confirm previous findings that the GRB rate at high redshift (z > 3) appears to be in excess of predictions based on assumptions that it should follow conventional determinations of the star formation history of the universe, combined with an estimate of its likely metallicity dependence. This suggests that either star formation at high redshifts has been significantly underestimated, for example due to a dominant contribution from faint, undetected galaxies, or that GRB production is enhanced in the conditions of early star formation, beyond that usually ascribed to lower metallicity.

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arXiv2012

The shallow-decay phase in both optical and x-ray afterglows of Swift GRB 090529A: Energy injection into a wind-type medium?

The energy injection model is usually proposed to interpret the shallow-decay phase in Swift GRB X-ray afterglows. However, very few GRBs have simultaneous signatures of energy injection in their optical and X-ray afterglows. Here, we report optical observations of GRB 090529A from 2000 sec to $\sim10^6$ sec after the burst, in which an achromatic decay is seen at both wavelengths. The optical light curve shows a decay from 0.37 to 0.99 with a break at $\sim10^5$ sec. In the same time interval, the decay indices of the X-ray light curve changed from 0.04 to 1.2. Comparing these values with the closure relations, the segment after 3$\times10^{4}$ sec is consistent with the prediction of the forward shock in an ISM medium without any energy injection. The shallow-decay phase between 2000 to 3$\times10^{4}$ sec could be due to the external shock in a wind-type-like medium with an energy injection under the condition of $ν_o < ν_c < ν_x$. However, the constraint of the spectral region is not well consistent with the multi-band observations. For this shallow-decay phase, other models are also possible, such as energy injection with evolving microphysical parameters, or a jet viewed off-axis,etc.

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arXiv2011

Pre-ALMA observations of GRBs in the mm/submm range

GRBs generate an afterglow emission that can be detected from radio to X-rays during days, or even weeks after the initial explosion. The peak of this emission crosses the mm/submm range during the first hours to days, making their study in this range crucial for constraining the models. Observations have been limited until now due to the low sensitivity of the observatories in this range. We present observations of 10 GRB afterglows obtained from APEX and SMA, as well as the first detection of a GRB with ALMA, and put them into context with all the observations that have been published until now in the spectral range that will be covered by ALMA. The catalogue of mm/submm observations collected here is the largest to date and is composed of 102 GRBs, of which 88 had afterglow observations, whereas the rest are host galaxy searches. With our programmes, we contributed with data of 11 GRBs and the discovery of 2 submm counterparts. In total, the full sample, including data from the literature, has 22 afterglow detections with redshift ranging from 0.168 to 8.2. GRBs have been detected in mm/submm wavelengths with peak luminosities spanning 2.5 orders of magnitude, the most luminous reaching 10^33erg s^-1 Hz^-1. We observe a correlation between the X-ray brightness at 0.5 days and the mm/submm peak brightness. Finally we give a rough estimate of the distribution of peak flux densities of GRB afterglows, based on the current mm/submm sample. Observations in the mm/submm bands have been shown to be crucial for our understanding of the physics of GRBs, but have until now been limited by the sensitivity of the observatories. With the start of the operations at ALMA, the sensitivity will be increased by more than an order of magnitude. Our estimates predict that, once completed, ALMA will detect up to 98% of the afterglows if observed during the passage of the peak synchrotron emission.

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arXiv2011

Diversity of multiwavelength emission bumps in the GRB 100219A afterglow

Context. Multi-wavelength observations of gamma-ray burst (GRB) afterglows provide important information about the activity of their central engines and their environments. In particular, the short timescale variability, such as bumps and/or rebrightening features visible in the multi-wavelength light curves, is still poorly understood. Aims. We analyze the multi-wavelength observations of the GRB100219A afterglow at redshift 4.7. In particular, we attempt to identify the physical origin of the late achromatic flares/bumps detected in the X-ray and optical bands. Methods. We present ground-based optical photometric data and Swift X-ray observations on GRB100219A. We analyzed the temporal behavior of the X-ray and optical light curves, as well as the X-ray spectra. Results. The early flares in the X-ray and optical light curves peak simultaneously at about 1000 s after the burst trigger, while late achromatic bumps in the X-ray and optical bands appear at about 20000 s after the burst trigger. These are uncommon features in the afterglow phenomenology. Considering the temporal and spectral properties, we argue that both optical and X-ray emissions come from the same mechanism. The late flares/bumps may be produced by late internal shocks from long-lasting activity of the central engine. An off-axis origin for a structured jet model is also discussed to interpret the bump shapes. The early optical bump can be interpreted as the afterglow onset, while the early X-ray flare could be caused by the internal activity. GRB 100219A exploded in a dense environment as revealed by the strong attenuation of X-ray emission and the optical-to-X-ray spectral energy distribution.

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arXiv2011

GRB091127/SN2009nz and the VLT/X-shooter spectroscopy of its host galaxy: probing the faint end of the mass-metallicity relation

We perform a detailed study of the gamma-ray burst GRB091127/SN2009nz host galaxy at z=0.490 using the VLT/X-shooter spectrograph in slit and integral-field unit (IFU). From the analysis of the optical and X-ray afterglow data obtained from ground-based telescopes and Swift-XRT we confirm the presence of a bump associated with SN2009nz and find evidence of a possible jet break in the afterglow lightcurve. The X-shooter afterglow spectra reveal several emission lines from the underlying host, from which we derive its integrated properties. These are in agreement with those of previously studied GRB-SN hosts and, more generally, with those of the long GRB host population. We use the Hubble Space Telescope and ground based images of the host to determine its stellar mass (M_star). Our results extend to lower M_star values the M-Z plot derived for the sample of long GRB hosts at 0.3<z<1.0 adding new information to probe the faint end of the M-Z relation and the shift of the LGRB host M-Z relation from that found from emission line galaxy surveys. Thanks to the IFU spectroscopy we can build the 2D velocity, velocity dispersion and star formation rate (SFR) maps. They show that the host galaxy has a perturbed rotation kinematics with evidence of a SFR enhancement consistent with the afterglow position.

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arXiv2011

The dark GRB080207 in an extremely red host and the implications for GRBs in highly obscured environments

[Abridged] We present comprehensive X-ray, optical, near- and mid-infrared, and sub-mm observations of GRB 080207 and its host galaxy. The afterglow was undetected in the optical and near-IR, implying an optical to X-ray index <0.3, identifying GRB 080207 as a dark burst. Swift X-ray observations show extreme absorption in the host, which is confirmed by the unusually large optical extinction found by modelling the X-ray to nIR afterglow spectral energy distribution. Our Chandra observations obtained 8 days post-burst allow us to place the afterglow on the sky to sub-arcsec accuracy, enabling us to pinpoint an extremely red galaxy (ERO). Follow-up host observations with HST, Spitzer, Gemini, Keck and the James Clerk Maxwell Telescope (JCMT) provide a photometric redshift solution of z ~1.74 (+0.05,-0.06) (1 sigma), 1.56 < z < 2.08 at 2 sigma) for the ERO host, and suggest that it is a massive and morphologically disturbed ultra-luminous infrared galaxy (ULIRG) system, with L_FIR ~ 2.4 x 10^12 L_solar. These results add to the growing evidence that GRBs originating in very red hosts always show some evidence of dust extinction in their afterglows (though the converse is not true -- some extinguished afterglows are found in blue hosts). This indicates that a poorly constrained fraction of GRBs occur in very dusty environments. By comparing the inferred stellar masses, and estimates of the gas phase metallicity in both GRB hosts and sub-mm galaxies we suggest that many GRB hosts, even at z>2 are at lower metallicity than the sub-mm galaxy population, offering a likely explanation for the dearth of sub-mm detected GRB hosts. However, we also show that the dark GRB hosts are systematically more massive than those hosting optically bright events, perhaps implying that previous host samples are severely biased by the exclusion of dark events.

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arXiv2011

GRB 070125 and the environments of spectral-line poor afterglow absorbers

GRB 070125 is among the most energetic bursts detected and the most extensively observed so far. Nevertheless, unresolved issues are still open in the literature on the physics of the afterglow and on the GRB environment. In particular, GRB 070125 was claimed to have exploded in a galactic halo environment, based on the uniqueness of the optical spectrum and the non-detection of an underlying host galaxy. In this work we collect all publicly available data and address these issues by modelling the NIR-to-X-ray spectral energy distribution (SED) and studying the high signal-to-noise VLT/FORS afterglow spectrum in comparison with a larger sample of GRB absorbers. The SED reveals a synchrotron cooling break in the UV, low equivalent hydrogen column density and little reddening caused by a LMC- or SMC-type extinction curve. From the weak MgII absorption at z=1.5477 in the spectrum, we derived logN(MgII)=12.96+0.13-0.18 and upper limits on the ionic column density of several metals. These suggest that the GRB absorber is most likely an LLS with a 0.03Z\odot<Z<1.3Z\odot metallicity. The comparison with other GRB absorbers places GRB070125 at the low end of the absorption line equivalent width distribution, confirming that weak spectral features and spectral-line poor absorbers are not so uncommon in afterglow spectra. Moreover, we show that the effect of photo-ionization on the gas surrounding the GRB, combined with a low N(HI) along a short segment of the line of sight within the host galaxy, can explain the lack of spectral features in GRB070125. Finally, the non-detection of an underlying galaxy is consistent with a faint GRB host galaxy, well within the GRB host brightness distribution. Thus, the possibility that GRB070125 is simply located in the outskirts of a gas-rich, massive star-forming region inside its small and faint host galaxy seems more likely than a gas-poor, halo environment origin.

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arXiv2011

A Photometric Redshift of z ~ 9.4 for GRB 090429B

Gamma-ray bursts (GRBs) serve as powerful probes of the early Universe, with their luminous afterglows revealing the locations and physical properties of star forming galaxies at the highest redshifts, and potentially locating first generation (Population III) stars. Since GRB afterglows have intrinsically very simple spectra, they allow robust redshifts from low signal to noise spectroscopy, or photometry. Here we present a photometric redshift of z~9.4 for the Swift-detected GRB 090429B based on deep observations with Gemini-North, the Very Large Telescope, and the GRB Optical and Near-infrared Detector. Assuming a Small Magellanic Cloud dust law (which has been found in a majority of GRB sight-lines), the 90% likelihood range for the redshift is 9.06 < z < 9.52, although there is a low-probability tail to somewhat lower redshifts. Adopting Milky Way or Large Magellanic Cloud dust laws leads to very similar conclusions, while a Maiolino law does allow somewhat lower redshift solutions, but in all cases the most likely redshift is found to be z>7. The non-detection of the host galaxy to deep limits (Y_AB >~ 28 mag, which would correspond roughly to 0.001 L* at z=1) in our late time optical and infrared observations with the Hubble Space Telescope strongly supports the extreme redshift origin of GRB 090429B, since we would expect to have detected any low-z galaxy, even if it were highly dusty. Finally, the energetics of GRB 090429B are comparable to those of other GRBs, and suggest that its progenitor is not greatly different to those of lower redshift bursts.

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arXiv2011

Spectroscopic evidence for SN 2010ma associated with GRB 101219B

We report on the spectroscopic detection of supernova SN 2010ma associated with the long gamma-ray burst GRB 101219B. We observed the optical counterpart of the GRB on three nights with the X-shooter spectrograph at the VLT. From weak absorption lines, we measure a redshift of z = 0.55. The first epoch UV--near-infrared afterglow spectrum, taken 11.6 hr after the burst, is well fit by a power law consistent with the slope of the X-ray spectrum. The second and third epoch spectra (obtained 16.4 and 36.7 days after the burst), however, display clear bumps closely resembling those of the broad-lined type-Ic SN 1998bw if placed at z=0.55. Apart from demonstrating that spectroscopic SN signatures can be observed for GRBs at these large distances, our discovery makes a step forward in establishing a general connection between GRBs and SNe. In fact, unlike most previous unambiguous GRB-associated SNe, GRB 101219B has a large gamma-ray energy (E_iso = 4.2 x 10^{51} erg), a bright afterglow, and obeys the "Amati" relation, thus being fully consistent with the cosmological population of GRBs.

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arXiv2011

An extremely luminous panchromatic outburst from the nucleus of a distant galaxy

Variable X-ray and gamma-ray emission is characteristic of the most extreme physical processes in the Universe, and studying the sources of these energetic photons has been a major driver in astronomy for the past 50 years. Here we present multiwavelength observations of a unique gamma-ray selected transient, discovered by Swift, which was accompanied by bright emission across the electromagnetic spectrum, and whose properties are unlike any previously observed source. We pinpoint the event to the center of a small, star-forming galaxy at redshift z=0.3534. Its high-energy emission has lasted much longer than any gamma-ray burst, while its peak luminosity was about 100 times higher than the brightest active galactic nuclei. The association of the outburst with the center of its host galaxy suggests that this phenomenon has its origin in a new, rare mechanism associated with a massive black hole in the nucleus of a galaxy.

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arXiv2011

Variable Ly alpha sheds light on the environment surrounding GRB 090426

Long duration gamma-ray bursts are commonly associated with the deaths of massive stars. Spectroscopic studies using the afterglow as a light source provide a unique opportunity to unveil the medium surrounding it, probing the densest region of their galaxies. This material is usually in a low ionisation state and at large distances from the burst site, hence representing the normal interstellar medium in the galaxy. Here we present the case of GRB 090426 at z=2.609, whose optical spectrum indicates an almost fully ionised medium together with a low column density of neutral hydrogen. For the first time, we also observe variations in the Ly alpha absorption line. Photoionisation modeling shows that we are probing material from the vicinity of the burst (~80 pc). The host galaxy is a complex of two luminous interacting galaxies, which might suggest that this burst could have occurred in an isolated star-forming region outside its host galaxy created in the interaction of the two galaxies.

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arXiv2010

The circumburst density profile around GRB progenitors: a statistical study

According to our present understanding, long GRBs originate from the collapse of massive stars while short bursts are due to the coalescence of compact stellar objects. Since the afterglow evolution is determined by the circumburst density profile, n(r), traversed by the fireball, it can be used to distinguish between a so-called ISM profile, n(r) = const., and a free stellar wind, $n(r) \propto r^{-2}$. Our goal is to derive the most probable circumburst density profile for a large number of Swift-detected bursts using well-sampled afterglow light curves in the optical and X-ray bands. We combined all publicly available optical and Swift/X-ray afterglow data from June 2005 to September 2009 to find the best-sampled late-time afterglow light curves. After applying several selection criteria, our final sample consists of 27 bursts, including one short burst. The afterglow evolution was then studied within the framework of the fireball model. We find that the majority (18) of the 27 afterglow light curves are compatible with a constant density medium (ISM case). Only 6 of the 27 afterglows show evidence for a wind profile at late times. In particular, we set upper limits on the wind termination-shock radius, $R_T$, for GRB fireballs which are propagating into an ISM profile and lower limits on $R_T$ for those which were found to propagate through a wind medium. Observational evidence for ISM profiles dominates in GRB afterglow studies, implying that most GRB progenitors might have relatively small wind termination-shock radii. A smaller group of progenitors, however, seems to be characterised by notably more extended wind regions.

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arXiv2010

A High Signal-to-Noise Ratio Composite Spectrum of Gamma-ray Burst Afterglows

We present a composite spectrum of 60 long duration gamma-ray burst (GRB) afterglows with redshifts in the range 0.35<z<6.7 observed with low resolution optical spectra. The composite spectrum covers the wavelength range 700-6600 A in the rest frame and has a mean signal-to-noise ratio of 150 per 1 A pixel and reaches a maximum of ~300 in the range 2500-3500 A. Equivalent widths are measured from metal absorption lines from the Lya line to ~5200 A, and associated metal and hydrogen lines are identified between the Lyman break and Lya line. The average transmission within the Lyman forest is consistent with that found along quasar lines of sight. We find a temporal variation in fine structure lines when dividing the sample into bursts observed within 2 hours from their trigger and those observed later. Other lines in the predominantly neutral gas show variations too, but this is most likely a random effect caused by weighting of individual strong absorption lines and which mimics a temporal variation. Bursts characterized with high or low prompt GRB energy release produce afterglows with similar absorption line strengths, and likewise for bursts with bright or faint optical afterglows. Bursts defined as dark from their optical to X-ray spectral index have stronger absorption lines relative to the optically bright bursts. The composite spectrum has strong CaII and MgII absorption lines as commonly found in dusty galaxies, however, we find no evidence for dust or a significant molecular content based on the non-detection of diffuse interstellar bands. Compared to starburst galaxy spectra, the GRB composite has much stronger fine structure lines, while metal absorption lines are weaker.

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arXiv2010

Probing GRB environments with time variability: ULTRASPEC fast imaging of GRB 080210

We present high time resolution (1.09 s) photometry of GRB 080210 obtained with ULTRASPEC mounted on the ESO/3.6-m telescope, starting 68.22 min after the burst and lasting for 26.45 min. The light curve is smooth on both short (down to 2.18 s) and long time scales, confirmed by a featureless power spectrum. On top of the fireball power-law decay, bumps and wiggles at different time scales can, in principle, be produced by density fluctuations in the circumburst medium, substructures in the jet or by refreshed shocks. Comparing our constraints with variability limits derived from kinematic arguments, we exclude under-density fluctuations producing flux dips larger than 1 per cent with time scales \Deltat > 9.2 min (2 per cent on \Deltat > 2.3 min for many fluctuating regions). In addition, we study the afterglow VLT/FORS2 spectrum, the optical-to-X-ray spectral energy distribution (SED) and the time decay. The SED is best fit with a broken power law with slopes βopt = 0.71 \pm 0.01 and βX = 1.59 \pm 0.07, in disagreement with the fireball model, suggesting a non-standard afterglow for GRB 080210. We find AV = 0.18 \pm 0.03 mag optical extinction due to SMC-like dust and an excess X-ray absorption of log (NH/cm-2) = 21.58 +0.18 -0.26 assuming Solar abundances. The spectral analysis reveals a damped Lyα absorber (log (NH I /cm-2) = 21.90 \pm 0.10) with a low metallicity ([X/H] = -1.21 \pm 0.16), likely associated with the interstellar medium of the GRB host galaxy (z = 2.641).

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